Although atom in Greek means indivisible, we now know that an atom can be broken into smaller parts. The atom is made of a nucleus surrounded by a cloud of electrons. The nucleus was discovered by Ernst Rutherford in 1911 who realized that it must be a very small and dense region inside the mostly empty atom. This nucleus can also be broken down into pieces called protons and neutrons. Those protons and neutrons are actually built up from quarks and gluons. These quarks and gluons don't like to be on there own. Similar to the saying that "absence makes the heart grow fonder", the further apart quarks and gluons are the more attracted they become to each other. This is a very unique property of the force between them called the strong force. Because of the strong force, we can't break a proton into pieces. But we can melt a bunch of protons and neutrons into a form of matter that hasn't existed since one microsecond after the big bang. This is the matter that exists if we heat and compress a bunch of protons and neutrons until they melt together into a soup of quarks and gluons called the quark gluon plasma (QGP). Inside the QGP, there are no protons and neutrons, just a seething mix of quarks and gluons in a soup that is 250,000 times hotter than the center of the sun. This matter is created thousands or even millions of times per second in the collision of gold nuclei at the RHIC, the Relativistic Heavy Ion Collider of Brookhaven National Laboratory.